Among stocks in the spotlight, Williams Partners
WPZ, -1.21%
agreed to buy natural gas gathering systems in the Marcellus shale of Pennsylvania and New York for $750 million. The seller is American Securities LLC.

Concho Resources
CXO, -1.02%
said it would pay Petroleum Development Corp.
PETD
about $175 million for producing and non-producing assets in the Wolfberry trend in the Permian Basin of Texas. The deal adds 10,800 gross acres in Andrews, Ector and Midland Counties, Texas. Concho will increased its 2012 capital budget to $1.4 billion from $1.3 billion to develop the new acreage.

Among small cap stocks, RAM Energy Resources Inc.
RAM, +11.98%
jumped 83% after Halcon Resources, a newly-formed company led by former Petrohawk Energy CEO Floyd Wilson, said it would invest $550 million in the firm. Wilson will become CEO of RAM Energy when the deal closes by the end of March.

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